And tomorrow, president obama will announce his action plan against gun violence in america. But today, new york governor andrew cuomo signed a law that is the toughest gun law in the nation right now and tried to tackle a very big question. How do you keep guns out of the hands of the mentally ill? Abc's senior justice correspondent pierre thomas tells us about the controversial idea. Reporter: We have all seen the faces. Young men accused of horrific mass shootings, looking unstable, believed to be mentally ill. They were ticking time bombs who sometimes had encounters with mental health professionals. Could they have been stopped? Today, new york state officials are leading the way, passing a new law they hope will block violent acts by the mentally ill. We must stop the madness and lead the way once again in saving lives. Reporter: The new law would require mental health professionals to report to state officials any patient they deem to be a "significant risk" or "threat." The law might have made a difference in shootings at virginia tech and a colorado movie theater. In both cases, the young men received mental health counseling. This would be a sea change but potentially opens up a huge number of patients to the that they're in treatment. People who are concerned about their privacy may decide not even to come to treatment in the first place. People with mental illness account for a very small pro portion of the violence that's committed. Reporter: But victims of mass shootings want something done yesterday about the mentally it's access to guns. They all have a common thread and it's all two parts. Mentally ill people with guns. Come on. It's a three that combination. Reporter: The question now -- will america follow new york's lead? Pierre thomas, abc news, washington.

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